A Night of Mystery was based on Ferreol, the famous crime novel by Victorien Sardou. While visiting the apartment of ex-lover Gilberte (
Evelyn Brent), Captain Ferreol (Menjou) witnesses a murder. The crafty killer persuades Ferreol not to report the crime, lest Gilberte's indiscretions be revealed to her husband. Ferreol discreetly leaves Paris and heads for Africa but returns when he learns that Gilberte's brother Jerome (William Collier Jr.) has been falsely accused of the murder. Still hoping to shield Gilberte from scandal, Ferreol confesses to the crime himself, but an inadvertent slip of the tongue clears both Ferreol and Jerome in one fell swoop. ~ Hal Erickson, All Movie Guide